Demo of overlay-able runtime configuration

[yfyf]

Things to decide on:

• What goes into the configuration?
• As discussed, "runtime" is probably not a perfect name
• Should the values be passed down to services (e.g. controller), or should they read them from the file? If the latter, how do we ensure they read only the defined values?

Checklist

• Changelog updated
• Code documented
• User manual updated

[knuton]

I would close this for now, it adds complexity and harm from baked in configuration during development has been at least reduced with the quick build option.

What do you think?

[yfyf]

I would close this for now, it adds complexity and harm from baked in configuration during development has been at least reduced with the quick build option.

What do you think?

Yes, it's probably the right thing to do, closing. Can revise if we develop a more pressing need.

Some extra notes: I think the fact that we do not separate "build" configuration from "runtime" / "channel" configuration is still problematic. It causes many needless rebuilds and overall lack of clarity of what parameters can influence what.

But this is kind of unavoidable in a nix system and this PR only covers some scenarios. For example, in #309, we need two bundles that are identical except for the versions. The approach used in this PR would NOT help, so it's not a comprehensive solution.